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Biomedical subjects

F Rojas

Publications and source records attributed to F Rojas.

At least 19 recordsLinked to original sources
PubMed2005

Azole resistance in neonatal intensive care units in Argentina.

The aim of this study was to determine the antifungal susceptibility profile and to detect resistant strains of yeast species isolated from neonates in Intensive Care Units. 92 strains isolated from 25 bloodstream cultures, 20 venous catheters, 23 suprapubic aspirations and 24 rectal swabs were studied. A Candida glabrata strain resistant to fluconazole was detected. Candida krusei appeared with its inherent resistance to fluconazole and showed cross-resistance to itraconazole. Two Candida albicans strains were resistant to azoles, one to itraconazole and the other to fluconazole with a high minimum inhibitory concentration (MIC) for itraconazole. All Candida tropicalis strains were susceptible to fluconazole but two of them showed resistance to itraconazole. The detection of resistant strains in neonates whom had not received previous antifungal therapy is noteworthy. The variations in the epidemiology of fungal infections observed and the antifungal resistance detected emphasize the importance of performing a regular surveillance to observe and to assess them.

Antifungal Agents↗
PubMed2004

Gene frequency distribution of the BoLA-DRB3 locus in Saavedreño Creole dairy cattle.

The objective of this study is to describe the gene frequency distribution of the bovine lymphocyte antigen (BoLA)-DRB3 locus in Saavedreño Creole dairy cattle and to compare it with previously reported patterns in other cattle breeds. One hundred and twenty-five Saavedreño Creole dairy cattle were genotyped for the BoLA-DRB3.2 allele by polymerase chain reaction and restriction fragment length polymorphism. Twenty-two out of 53 previously identified BoLA-DRB3.2 alleles were detected, with gene frequencies ranging from 0.4 to 16.8%. Seventy percent of the variation corresponded to the seven most frequent alleles (BoLA-DRB3.2*7, *8, *11, *16, *27, *36, and *37). The studied population exhibits a high degree of expected heterozygosity (he = 0.919). The FIS index did not show significant deviation from Hardy-Weinberg equilibrium. However, the neutrality test showed an even gene frequency distribution. This result could be better explained assuming balancing selection instead of neutral or positive selection for one or a few alleles. In conclusion, the results of this study demonstrated that BoLA-DRB3.2 is a highly polymorphic locus in Saavedreño Creole dairy cattle, with significant variation in allele frequency among cattle breeds.

Alleles↗
PubMed2004

Yeasts species distribution in Neonatal Intensive Care Units in northeast Argentina.

The aim of this study was to determine the distribution and antifungal susceptibility profile of yeast species isolated from neonates in Neonatal Intensive Care Units (NICU) in northeast of Argentina. With this purpose 92 strains isolated from 25 blood stream cultures, 20 venous catheters, 23 suprapubic aspirations and 24 rectal swabs were studied. Candida albicans and C. parapsilosis appeared with similar frequencies (36%) in blood stream isolates. Candida parapsilosis (50%) was the most frequent catheters colonizer and C. tropicalis (54.2%) was the most frequent yeast associated with gastrointestinal tract colonization. Candida krusei, C. glabrata and Trichosporon cutaneum appeared with a very low frequency. A high rate of susceptibility to amphotericin B, fluconazole, and itraconazole was observed.

Antifungal Agents↗
PubMed2002

Comparative immunohistochemical study of normal, hyperplastic and neoplastic C cells of the rat thyroid gland.

In rats, the frequency of spontaneous C-cell tumours is very high and is both age and gender dependent. The three specific stages of neoplastic progression can be distinguished into diffuse C-cell hyperplasia, focal C-cell hyperplasia and bona fide C-cell tumours. Based on this hypothetical model of human medullary thyroid carcinoma (MTC), we carried out an immunohistochemical study using different markers (calcitonin, calcitonin gene-related peptide, somatostatin and chromogranin) to verify the existence of any relationship between their expression and the successive steps of tumour development. We found a characteristic immunohistochemical staining pattern, particularly for calcitonin and somatostatin, which distinguishes C-cell tumours from both normal and hyperplastic C cells, with no differences related to the gender of the animals under study. Specifically, a considerable heterogeneity in calcitonin expression was only displayed by C-cell carcinomas, being less pronounced in C-cell adenomas. As for somatostatin, this regulatory peptide was found only in a minority of calcitonin-positive cells in normal and hyperplastic glands. However, in some C-cell adenomas and most C-cell carcinomas nearly all calcitonin-positive cells also coexpressed somatostatin. We conclude that rat C-cell neoplasms constitute a very particular tumour entity which shares many but not all immunohistochemical features with human MTC.

Adenoma↗
PubMed2001

Fluorescence polarization assay for the diagnosis of bovine brucellosis: adaptation to field use.

A fluorescence polarization assay (FPA) was used to test whole blood samples prepared by mixing blood cells from cattle without exposure to Brucella abortus (B. abortus) with sera from animals with confirmed (bacteriologically) infection. A cut-off value between negative and positive values was initially established to be 87.2mP. This value was changed to 95mP to increase assay specificity without loss of sensitivity when testing blood samples from negative animals. The FPA technology was applied to whole blood samples in the field and to stored whole blood samples using two diluent buffers. Relative sensitivity and specificity values for the FPA performed in the field, based on buffered antigen plate agglutination test and competitive enzyme immunoassay results were 95.3 and 97.3%, respectively. However, to obtain maximum sensitivity and specificity, a cut-off value of 105mP was determined for fresh whole blood samples. The relative sensitivity and specificity values of the FPA when testing stored whole blood samples were 100% each using a 95mP cut-off.The usefulness of the FPA for testing whole blood samples in the field was demonstrated.

Agglutination Tests↗
PubMed2000

Anion protection of CuZnSOD during peroxidative activity with H(2)O(2).

The "peroxidase" activity of the copper-zinc superoxide dismutase is a poorly sustained activity because of the competing inactivation of the enzyme. New evidence suggests that the bound oxidant may be partitioning between oxidizing the enzyme or oxidizing small anions. At constant peroxide, nitrite and azide only partially protect the enzyme (50%) against loss of copper(I) and inactivation up to one anion per copper. Beyond that level, there is no further protection. Bicarbonate ion also protects, but larger amounts are required. These data suggest that there is significant oxidation of the enzyme even in the presence of the small anions and therefore the formation of the bound oxidant cannot be sustained in a true catalytic process.

Animals↗
PubMed2000

Catecholamines-evoked cytosolic Ca2+ rise in endothelial cells from bovine adrenal medulla.

The effects of catecholamines on intracellular Ca2+ concentrations ([Ca2+]i) in single acutely dissociated bovine adrenal medulla endothelial cells (BAMECs) were measured using the intracellular fluorescent probe Fluo-3 AM. 100 microm epinephrine or norepinephrine induced a biphasic [Ca2+]i rise with an initial peak followed by a delayed phase. 10 microm phenylephrine (alpha1-adrenergic agonist) caused a [Ca2+]i rise similar to that evoked by catecholamines. The increase in [Ca2+]i induced by 10 microm phenylephrine was reverted by 10 microm phenoxybenzamine (alpha-adrenergic antagonist). Neither isoproterenol (beta-adrenergic agonist) nor clonidine (alpha2-adrenergic agonist) induced [Ca2+]i rise. The initial peak was insensitive to zero external Ca2+ and it was abolished after Ca2+ internal storages were emptied by 10 mM caffeine. The delayed phase was reduced to near zero by external Ca2+ removal. These results indicate that BAMECs possess alpha1-adrenergic receptors associated to both the release of caffeine-sensitive intracellular Ca2+ stores and the entry of extracellular Ca2+. We suggest that chromaffin cell secretion may activate BAMECs in vivo through an increase in [Ca2+]i which could induce the secretion of vasoactive factors allowing a rapid entry of hormones into the circulation.

Adrenal Medulla↗
PubMed2000

Ototoxicity caused by cisplatin is ameliorated by melatonin and other antioxidants.

The mechanism of the ototoxicity caused by cisplatin is based in the generation of reactive oxygen species, which interferes with the antioxidant protection of the organ of Corti. Conversely, the protection of the cochlea with antioxidants ameliorates the ototoxicity by cisplatin. The ototoxicity produced by cisplatin can be reversible or persistent, depending on the age of the patient, cumulative doses, number of chemotherapy cycles, history of noise exposure, and deteriorating renal function. We have obtained in rats an ototoxic chart utilizing cisplatin (10 mg/kg body weight injected intraperitoneally, once only). Together with this treatment, the animals were treated with melatonin in the drinking water (10 mg/L) or injected subcutaneously (250 microg), and with an antioxidant mixture, injected subcutaneously, composed of 0.25 mg alpha-tocopherol acid succinate, 3 mg ascorbic acid, 1 mg glutathione, and 60 mg N-acetylcysteine. The distortion product otoacoustic emissions were determined for a prolonged period of time for each animal. The ototoxicity produced by cisplatin was maximal from days 7 to 10 post-treatment, returning to normal values in a month. When melatonin and the antioxidant mixture were present, the recovery was between days 10 and 15 post-treatment, independent of the means of administration of the pineal product. We conclude that the ototoxicity caused by cisplatin is ameliorated by melatonin and other antioxidants.

Animals↗
PubMed1999

Electrochemical treatment of human KB cells in vitro.

Electrochemical treatment (ECT) of cancer is a promising new method by which direct current is delivered into tumor tissue to induce tumor regression. The purpose of this study is to evaluate the effectiveness of ECT on human cancer cells and to investigate the factors that affect ECT. The biological mechanisms of ECT in cancer treatment were also explored. Using human KB cells, ECT was found to delay cell growth by using 0.3 coulombs (C)/ml (1.5 C in 5 ml of culture medium; 3 V, 400 microA for 62.5 min). From the results of a colony-forming assay, it was clearly demonstrated that increasing the ECT dose decreases tumor cell survival. A cytotoxicity study, in which a methylene blue assay was used, determined that, for 2.5 x 10(5) cells in culture, the 1D50 was 0.68 C/ml. For a fixed dose of 0.6 C/ml (3 C in 5 ml), using higher current and shorter treatment time resulted in better cell survival. Time, therefore, is an important factor. When cell concentration was altered, the survival was higher for increased cell concentrations. A thymidine incorporation assay indicated that the amount of [3H]thymidine incorporated into DNA decreased as the ECT dose increased. After treatment with 1 C/ml (5 C in 5 ml; 3 V, 400 microA for 208.4 min), pH at the anode decreased to 4.53 and at the cathode increased to 10.46. These results indicate that ECT is effective for killing human KB cells in vitro and that the toxicity effect is related to charge, current, and treatment time. The effect of pH alteration on cells is one of the mechanisms of ECT.

Cell Division↗
PubMed1999

Political analysis of health reform in the Dominican Republic.

This article examines the major political challenges associated with the adoption of health reform proposals, through the experience of one country, the Dominican Republic. The article briefly presents the problems of the health sector in the Dominican Republic, and the health reform efforts that were initiated in 1995. The PolicyMaker method of applied political analysis is described, and the results of its application in the Dominican Republic are presented, including analysis of the policy content of the health reform, and assessment of five key groups of players (public sector, private sector, unions, political parties, and other non-governmental organizations). The PolicyMaker exercise was conducted in collaboration with the national Office of Technical Coordination (OCT) for health reform, and produced a set of 11 political strategies to promote the health reform effort in the Dominican Republic. These strategies were partially implemented by the OCT, but were insufficient to overcome political obstacles to the reform by late 1997. The conclusion presents six factors that affect the pace and political feasibility of health reform proposals, with examples from the case of the Dominican Republic.

Developing Countries↗
PubMed1999

Dynamical scaling: the two-dimensional XY model following a quench.

To sensitively test scaling in the two-dimensional XY model quenched from high temperatures into the ordered phase, we study the difference between measured correlations and the (scaling) results of a Gaussian-closure approximation. We also directly compare various length scales. All of our results are consistent with dynamical scaling and an asymptotic growth law L approximately (t/ln[t/t(0)])(1/2), though with a time scale t(0) that depends on the length scale in question. We then reconstruct correlations from the minimal-energy configuration consistent with the vortex positions, and find them significantly different from the "natural" correlations - though both scale with L. This indicates that both topological (vortex) and nontopological "spin-wave" contributions to correlations are relevant arbitrarily late after the quench. We also present a consistent definition of dynamical scaling applicable more generally, and emphasize how to generalize our approach to other quenched systems where dynamical scaling is in question. Our approach directly applies to planar liquid-crystal systems.

Journal Article↗
PubMed1999

Melatonin and other antioxidants prolong the postmortem activity of the outer hair cells of the organ of Corti: its relation to the type of death.

The outer hair cells of the organ of Corti transform sound into electrical signals, beginning the nervous auditive process. These cells produce acoustic emissions when working routinely, known as otoacoustic emissions. Otoacoustic emissions (OAEs) are recorded from the hearing duct through a probe which incorporates a sound source and a sensitive microphone. On the other hand, the cochlea produces oxygen-derived free radicals and nitric oxide, in addition, melatonin is present in the cochlea. The authors have studied the influence of melatonin or an antioxidant mixture (alpha-tocopherol acid succinate, ascorbic acid, glutathione, and N-acetylcysteine) on the postmortem activity of the outer hair cells of the organ of Corti of the rat, measuring distortion product otoacoustic emissions. Control rats showed postmortem distortion product otoacoustic emissions for about 2 min when sacrificed by decapitation, and for about 3 min when sacrificed by chloroform inhalation. Melatonin prolonged the postmortem activity 3.5 times when the animals were sacrificed by decapitation, and 7 times when animals were sacrificed by chloroform inhalation. Similar results were obtained with the antioxidant mixture. Results show that melatonin and other antioxidants have, in general, a protective role on the postmortem activity of the outer hair cells of the organ of Corti.

Animals↗
PubMed1993

Mycoflora and toxigenic Aspergillus flavus in Spanish milks.

The isolation, enumeration and identification of moulds were carried out on 64 samples of raw milk and 33 of pasteurized milk. The genera most frequently isolated in the raw milk were: Geotrichum (76.5%), Fusarium (45.3%), and Aspergillus (31.2%). In pasteurized milk they were: Aspergillus (61.5%) followed by Fusarium and Penicillium (37.7% in both cases). A. flavus was found in 12 samples and 1 out of the strains examined produced aflatoxins in vitro. The effect of pasteurization of the milk on spores of A. parasiticus NRRL-2999 was examined. The presence of moulds in pasteurized milk seems to be explained by contamination during bottling.

Aflatoxins↗